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fxus63 kpah 210548 

Area forecast discussion
National Weather Service Paducah Kentucky
1148 PM CST Wed Nov 20 2019

issued at 1148 PM CST Wed Nov 20 2019

Updated aviation section for 06z tafs.


Short term...(tonight through Friday night)
issued at 322 PM CST Wed Nov 20 2019

Ridging aloft today over our region will give way to west-
southwesterly mid level flow and southerly/southwesterly low level
flow tonight. Clouds will continue to increase from the west as a
mid level shortwave, with most of its energy focused across the
upper Midwest, moves across the pah forecast area from the
southwestern Continental U.S.. due to modest lift in our area, pcpn will be
in the form of light rain initially, with most of it occurring in
the morning hours of Thu as the mid level ridge over US begins to
rebound in the afternoon, decreasing updraft strength.

Thu night, a surface cold front is progged to settle into the
area, and at the same time, an overrunning mid level flow pattern
will set up ahead of the ejecting mid level low moving out of the
Central Plains, enabling plenty of deep moisture to be lifted
over our region. At this time, it appears the best quantitative precipitation forecast will be
overnight Thu/early Fri as widescale lift of up to 1.5 inch
precipitable water will occur especially near the Arkansas/Tennessee state
lines. This is about 2 Standard deviations above average for this
time of year. Thus, over an inch of rain is forecast to occur
there in a relatively brief period mainly between midnight Thu
and midday Fri, tapering down to lesser amounts farther north.
Forecast storm totals range from nearly two inches near the
southern border to less than half an inch north of Interstate 64.
This is not generally regarded as flash flood territory, but there
may be a few minor flooding issues where drainage is hindered by
accumulated leaves on the ground.

A lull in the rainfall is possible Fri afternoon, especially in
the northern parts of the region, followed by a resurgence in
scattered shower activity associated with the approaching Central
Plains low and its surface reflection, which may take a path
across the southern pennyrile region, or farther southeast,
according to differing model solutions. Despite lows in the 30s
Fri night, a wintry mix appears unlikely late due to warm air
aloft. Expect a general downward trend in temps with time.

Long term...(saturday through wednesday)
issued at 322 PM CST Wed Nov 20 2019

Active weather pattern will continue into early next week. A rather
strong system will exit our region Saturday, then another vigorous
storm system will influence our weather by the middle of next week.

On Saturday, a deepening low pressure center will pass across middle
Tennessee in the morning, then continue northeast away from our
region. Some rain will linger during the morning, mainly east of the
Mississippi River. An elevated warm layer aloft should prevent any
mix of frozen precip. Both the NAM and GFS indicate wet bulb temps
from 3 to 5 degrees celsius over southern Illinois and southeast MO within
the warm layer at 12z Sat. The afternoon will be mainly dry, but
clearing will be slow to occur. Extensive cloudiness and low level
cold advection will keep highs mainly in the 40s.

A period of dry conditions is expected from Saturday night through
Monday. The upper level flow will gradually become zonal over the
weekend, then turn southwesterly Monday as a 500 mb trough amplifies
over The Rockies. Highs will remain quite cool, generally in the
lower to mid 50s on Monday.

On Tuesday, the upper level trough will become negatively tilted as
it crosses the plains. Most of the guidance points to a deepening
surface low over the Central Plains on Tuesday, which moves
northeast across the Great Lakes Wednesday. The more southern track
of the 12z ECMWF appears to be an outlier, even compared to its own
ensemble mean from last night. The forecast will follow the more
northern low track, which means a mild southerly flow Tuesday for
our area. There is some potential for thunder if that track
verifies, but thunder potential is still too low to include in the
forecast. Depending on the intensity of the storm, strong gradient
winds and heavy rainfall could be hazards. Fortunately, quieter
weather is expected on Wednesday, the busiest travel day of the


issued at 1148 PM CST Wed Nov 20 2019

Isolated rain showers will be possible before sunrise, but main area of
showers will move west to east during the morning/early afternoon
hours. Cigs will lower quickly, becoming MVFR in the west during
the morning and progressing east to encompass the entire area by
later afternoon. Low level wind shear is a concern this morning, mainly between
09-16z. On the back side of the shower activity, a period of
gusty southwesterly winds of 25-30 kts is expected. A lull in
precipitation is expected during the afternoon, before increasing
again from the southwest during the evening. Lower MVFR cigs,
with possibly some IFR conditions are expected with this second
batch, along with reduced vsbys into MVFR territory. Winds will
become northwest late in the period and just beyond as a cold
front moves through.


Pah watches/warnings/advisories...


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